5870 Bottleneck Investigation (CPU and/or Memory Bandwidth)

[Astennu]

I haven't found any reference for this to be true no where dose it say you can only enable 1 of 5 parts of the SIMD.

Its depents on the game and the driver you can see it like this:



So if instructions can be grouped together you can have quite a performance boost. Down side is if you cant group instructions you only have 1/4e or 1/5e of the performance.

I dont know if its true but i have heard the AMD compiler does a quite good job. Grouping up to 3-4 of them most of the time.

But if you have a heavy nVidia optimised game you can have lower value's and bad shader performance. (you might it 1-3 then)


Then about the performance of the HD5870. It does not seem to me memory bandwith limited. But i also think there is more performance inside this core then we see now. It might be driver related. It wont surprise me if we get up to 20% higher performance in the future.

The RV870 core is still new. And i think AMD could optimize the scheduling of the threads a bit better so you can keep those 1600 alu's fed with data. It would be nice if there was a way to see the load on those shader units. And compare it to the load on RV770 and RV790 cores. Dont forget those are well optimized in the last years driver releases.